Cup making machines, such as those manufactured by Paper Machinery Corporation of Milwaukee, Wis., are used to make a variety of cups and containers. A typical cup machine for making paperboard cups, for instance, includes a turret having a plurality of mandrels about which the containers are formed. The turret sequentially rotates the mandrels into cooperation with a variety of workstations where numerous cup forming procedures sequentially occur. In an exemplary procedure, the circular bottom blank is cut at one workstation and attached to the end of a mandrel by a vacuum applied to the mandrel. During this procedure, the outside edge or lip of the bottom blank is folded downwardly. At a subsequent workstation, a sidewall blank is wrapped around the mandrel. The sidewall blank is heated and sealed along a seam which runs generally longitudinally along the side of the cup. (Typically, the paperboard is coated with a thermoplastic material, such as polypropylene, so the blanks may be heated and sealed together.)
The sidewall blank extends transversely to the bottom blank except along the lip which runs approximately parallel with the sidewall blank. In some applications, the sidewall blank includes a flap extending beyond the lip of the bottom blank, and this flap is bent over the lip. At a bottom finishing station, the flap is pressed against the lip from an inside recessed area at the bottom of the cup to seal the sidewall blank and bottom blank together.
There also may be other workstations where various additional cup forming procedures are carried out. For example, one station may be used to create a curl at the top of the cup to provide a more functional drinking container and a better appearance.
At a typical bottom blank maker workstation, a narrow web of bottom blank material, such as paperboard, is fed into the workstation and bottom blanks of desired size and configuration are cut by pressing the web against a cutting edge. Often, the cutting edge is circular in shape to cut disk-like bottom blanks for use in conventional paper cups. After cutting, a "draw" forces the bottom blank through a sleeve or opening sized somewhat smaller than the bottom blank. For example, with disk shaped blanks, the sleeve will be cylindrical in shape and has a diameter smaller than that of the bottom blank. Thus, as the draw forces the bottom blank through the sleeve, an outer edge or lip is folded over to an orientation generally transverse to the remainder of the bottom blank.
The folded bottom blank is forced through the sleeve into engagement with an adjacent mandrel that holds the blank in place via vacuum applied through apertures in its outer end. Subsequently, the turret rotates the bottom blank to another workstation where the sidewall blank is wrapped about the mandrel with a portion or flap extending beyond the lip of the bottom blank. This flap is folded over the lip of the bottom blank to create a recessed area in the bottom of the cup. This bottom area of the cup is heated and a finisher wheel is inserted into the recessed area and moved laterally against the flap to squeeze the flap, bottom blank lip and lower outside region of the sidewall together to form a seal about the bottom of the cup.
A problem that develops in conventional bottom blank maker workstations is the uneven creasing in the lip region which results from its being folded over and slid through the sleeve. Some of the creases resulting from this folding process can be sufficiently large to leave gaps even after the finisher wheel squeezes the lip portion between the flap and lower region of the sidewall blank. This, of course, results in a leaky container or cup.
Another problem that develops with conventional bottom blank maker stations is accumulation of debris, such as paperboard dust and lubricant in the mechanism. Often, the draw will be slidably mounted within a punch unit used to press the bottom blank web against the cutting edge to cut the bottom blank. Because these parts are constantly moving with respect to each other, it is common to use an appropriate lubricant between the components. However, as the bottom blanks are cut and forced through the sleeve, paper dust and lubricant accumulate between the punch and the draw. If enough debris accumulates, it can interfere with the operation of both the draw and the punch. Thus, periodically the machine must be inspected and cleaned of this accumulated debris.
It would be advantageous to provide a bottom blank maker workstation that controlled the creasing of the outer lip while providing for automatic cleaning of accumulated debris.